Several people have been reported killed or wounded in heavy clashes between rival warlords in northern Afghanistan.

The fighting broke out on Tuesday in the towns of Sar-e-Pol and Shulgara - near Mazar-e-Sharif - between ethnic Tajik commander Atta Mohammad and his main rival in the area, Abdul Rashid Dostum - an ethnic Uzbek.

Dostum is very influential in Mazar

The Afghan defence ministry said it had sent negotiators to the area on Wednesday to calm the situation.

Ashraf Nadim, a spokesman for General Atta, said a ceasefire had been negotiated in Shulgara but fighting was continuing around Sar-e-Pol.

The casualties were said to be mainly among the forces of General Atta, who is governor of Mazar.

General Dostum, who is Deputy Defence Minister as well as interim leader Hamid Karzai's special representative in the area, is also extremely influential in the city.

The clashes are thought to have arisen from a dispute about a military parade there on Sunday.

Mazar was the scene of bitter fighting between the two factions for several years before the Taleban seized control in 1998.

And there were further clashes after the Taleban departure as Uzbek and Tajik forces battled for control of the area at the end of January this year.

Eastern operation

Meanwhile, there are unconfirmed reports that hundreds of coalition soldiers have launched a large operation in eastern Afghanistan.

They are said to be targeting Taleban and al-Qaeda fighters in the mountains in Paktia province.

The operation began late on Tuesday in the Mezai mountains, 30 km (19 miles) east of the provincial capital Gardez, the Pakistan-based Afghan Islamic Press said.

The area is controlled by the Zadran tribe of senior Taleban military commander Jalaluddin Haqqani.

The raid follows the killing of four al-Qaeda fighters in the Khost region, next to Paktia, early on Tuesday.

The latest clashes come amid fears that al-Qaeda may try to use the improving weather in Afghanistan to launch a spring offensive.

Power struggles

The location of the fighting has added weight to reports that many Taleban and al-Qaeda fighters have moved to areas near the Pakistani border.

Afghan fighters have been backing the coalition assault force

US-led forces now appear to be concentrating their search in the border area where caves often start in Afghanistan and end in Pakistan.

The latest clashes happened in the same region where the last major battles against the Taleban and al-Qaeda were fought in March during Operation Anaconda.

There are now thousands of American, British and other coalition troops in Afghanistan.

Gardez fighting

Paktia province is another area of conflict between rival warlords.

Thirty people died last weekend when 500 rockets were fired into the provincial capital of Gardez.

Former king Zahir Shah, who returned to Afghanistan from exile last month, has sent a delegation to Gardez to mediate between the rivals - Padsha Khan and local governor Taj Mohammad Wardak.

The BBC's Lyse Doucet says Zahir Shah is still held in great esteem in the area, which is dominated by his fellow Pashtuns.

General Dostum, for his part, urged other senior Afghans to accept the authority of the former king.

"If we could have sorted out our problems ourselves he would not have had to return," he told the BBC.